Hi Leo,
For really good info on Top Bar Hives (TBH) I suggest you take a look at
http://www.biobees.com/forum/ You'll find yourself talking to folks who range from just starting to old hands and will be able to answer any questions you might have.
Probably the biggest problem with using these hives is that as a newcomer to beekeeping you really need the support of at least another beekeeper and probably a local society, They will undoubtedly tell you to use National hives to be compatible with their kit so they can help you with various problems you might have.
I've been keeping bees for about ten years now and have a TBH awaiting some bees. probably too late for this year, but you never know. They do seem to offer a wide variety of advantages to conventional hives - especially for the small scale beekeeper. Not least of which is not needing a centrifugal extractor which start at Thornes at about £160. Just cut the comb off and eat it or put it into a muslin bag and squeeze the honey out and make candles with the wax.
You might be well advised to start with a National with which to become familiar with bees and then move onto a TBH as you may well decide beekeeping isn't for you. In which case a National is always going to be more saleable than a TBH. You'll also get far more support from the old guard within your local association if using a National.
I hope you do decide to give it a go, as the more beekeepers there are the better it is for bees. I assure you, your first jar of honey is nearly as exciting as collecting and hiving your first swarm.
Good luck
Al